a = 1.28(d - c)/(1 - d/100)
a = amount of oil you need to add (in oz)
d = desired oil percentage (use 20 for 20%, for example)
c = current oil percentage (use 16 for 16%, for example)
So you if you want d = 20 (20% oil), c = 16 (actually you have 16% oil) result a = 6.4 (ie, add 6.4 oz of oil to each gallon of fuel).
Note that by adding oil, you&39;re reducing your nitro % a little. My figures show that my nitro is now down to about 14.3%... Seems to be a good trade.